Electrochemical sensors may be used to monitor the concentrations of species in various environments. For example, an electrochemical NOx sensor may be used to detect the concentration of nitrogen oxide emissions (collectively “NOx”) in the exhaust from an internal combustion engine. NOx sensors generally function by electrochemically dissociating NOx molecules and measuring a resulting ionic current through a solid electrolyte. Interfering species such as oxygen may be removed from the analytical environment within the sensor via electrochemical pumping to reduce the impact of such species on a NOx concentration measurement.
As NOx emission standards become more restrictive, sensor accuracy becomes increasingly important to provide accurate feedback for controlling processes and parameters related to emissions control. However, measuring low levels of NOx accurately can be difficult, as residual oxygen levels may cause offset errors in the NOx measurement. Furthermore, these effects may vary with oxygen concentration, water vapor concentration, electrode polarization effects due to sensor ageing and/or defects, etc.
The inventors herein have recognized that the accuracy of an electrochemical sensor such as a NOx sensor may be improved by obtaining a measurement of an interfering species at a location spatially adjacent to a measuring electrode of the measuring electrode pair, and adjusting one or more of an operation or an output processing of the electrochemical gas sensor based on the measurement of the interfering species. In this manner, the measurement of the interfering species may be used to adjust the removal rates of the interfering species and/or to adjust an offset of an analyte measurement to compensate for the presence of the interfering species.